Comparison of transport properties between Tl-(1223) and Tl-(2223) phases of Tl-Ba-Ca-Cu-O systems

Thin films of the (1223) phase (Tl-(1223), single Tl-O layer) and the (2223) phase (Tl-(2223), double Tl-O layers) of the Tl-Ba-Ca-Cu-O system were prepared using the laser ablation method. Both films had a high transport critical current density (J sub(c)) of 1.5x10 super(5) A/cm super(2) at 77 K in zero magnetic field. When the magnetic field was applied parallel to the a-b plane (a-b plane parallel B), transport properties in both films at different temperatures were similar. On the other hand, in fields perpendicular to the a-b plane (a-b plane perpendicular B), J sub(c) of the Tl-(1223) thin film was higher than that of the Tl-(2223) thin film at 40, 60 and 77 K. The irreversible magnetic fields (B sub(c2)* values) obtained from the resistivity change in the magnetic fields were 8.0 and 2.0 T at T/T sub(c) = 0.6 for the Tl-(1223) and Tl-(2223) thin films, respectively. These results suggested that the thickness of the Tl-O layer, which is non superconductive, determines transport properties for fields applied perpendicular to the a-b plane.